Tuberculosis (TB)
| Characteristics | |
|---|---|
| Morphology | The bacteria that cause tuberculosis (TB) are acid-fast (stain Gram positive), aerobic, non-spore forming, non-motile bacteria. Forming slightly curved or straight rods which may branch (0.2 to 0.6 µm by 1.0 to 10 μm), they are slow growers and require more than 7 days to form visible colonies. The majority of tuberculosis (TB) cases in people are caused by Mycobacterium tuberculosis (M. tuberculosis). Mycobacterium bovis (M. bovis) is another mycobacterium that can cause TB disease in people, but it is only responsible for fewer cases (less than 2%) compared to M. tuberculosis. |
| Growth Conditions | M. tuberculosis is sub cultured in Lowenstein-Jensen medium; Middlebrook 7H10 medium is used for M. bovis sub culture |
| Health Hazards | |
|---|---|
| Host Range | Primarily found in humans but has been seen in cattle, non-human primates, and other mammals (both wild and domestic) |
| Modes of Transmission | Transmission can be nosocomial or airborne (coughing and sneezing). Other modes of transmission include exposure to autopsy material, venereal transmission, and even percutaneous transmission. Bovine tuberculosis can occur from exposure to infected cattle, unpasteurized dairy products, or during the hunting and slaughter of infected animals |
| Signs and Symptoms | Nausea, weakness, fatigue, prolonged cough, chest pain, rapid weight loss, fever, night sweats, hemoptysis (blood in sputum). Miliary (disseminated) tuberculosis has the most serious consequences with meningitis developing in 50% of cases, along with a high fatality rate if not treated effectively. HIV infection is a serious risk factor for the development of active disease. For M. bovis infections, but all progress to TB disease, so there might be no symptoms at all. In people, symptoms of TB disease caused by M. bovis are similar to the symptoms of TB caused by M. tuberculosis |
| Infectious Dose | M. tuberculosis has a very low infectious dose, the ID50 is estimated to be <10 bacilli in humans. Similar infectious doses appear in M. bovis exposures |
| Incubation Period | 4-6 weeks, in latent TB infections, 5% of patients develop an active infection within 2 years and 5% develop an infection within their lifetime |
| Medical Precautions/Treatment | |
|---|---|
| Prophylaxis | For persons latently infected with TB, Isoniazid is primarily used. Exposure without infection (reactive skin test) is typically not treated unless the person is immunocompromised or pregnant. |
| Vaccines | None publically available |
| Treatment | Antibiotic treatment is available, but determining the resistance of the strain is crucial to prescribing the correct treatment method |
| Surveillance | Monitor for symptoms. Annual or semi-annual skin testing with purified protein derivative (PPD) or FDA-approved Interferon-Gamma Release Assay (IGRA) of previously skin-test-negative personnel can be used as a surveillance procedure. Direct smear microscopy or chest x-ray can detect positive cases |
| GWU Requirements | Report all incidents to the Office of Risk Management as well as the Office of Research Safety (ORS) IMMEDIATELY FOLLOWING THE OCCURRENCE. |
| Containment | |
|---|---|
| BSL-2 | Risk Group 3 classification is applied to both agents of TB. BSL-2 practices and procedures, containment equipment, and facilities are recommended for non-aerosol-producing manipulations of clinical specimens. Manipulation of small quantities of the attenuated vaccine strain M. bovis Bacillus Calmette-Guérin (BCG) can be performed at the BSL-2 level |
| ABSL-2+ | Animal studies using rodents (e.g., guinea pigs, rats, rabbits, mice) can be conducted at ABSL-2 with ABSL-3 practices. |
| BSL-3 | BSL-3 practices, containment equipment, and facilities are recommended for laboratory activities in the propagation and manipulation of cultures of any of the subspecies of the M. tuberculosis complex. Use of a slide-warming tray, rather than a flame, is recommended for fixation of slides. |
| ABSL-3 | ABSL-3 practices are recommended for animal studies using experimentally or naturally infected NHPs or immunocompromised mice, as high titers may be found in organs from immunocompromised animals. All airborne infections of rodents using the M. tuberculosis complex must be performed in an appropriate ABSL-3 laboratory. |
| Spill Procedures | |
|---|---|
| Small Spills (<1 liter) | If the spill occurred inside a biological safety cabinet, close the sash and allow the cabinet to operate for 15 minutes before continuing with the spill cleanup.
TB can very easily be aerosolized and contaminate surrounding surfaces, caution should be taken during a spill outside of a BSC. Leave the room immediately and allow the aerosols to dissipate for 15 minutes. Notify others working in the lab. Don appropriate PPE. Cover area of the spill with paper towels or any absorbent material and apply an EPA registered disinfectant effective against the bacteria (bleach, peroxyacetic acid, cavicide, phenolics), working from the perimeter towards the center. Allow 30 minutes of contact time before disposal and cleanup of spill materials. |
| Large Spills | Alert lab personnel in the laboratory to the spill and keep people out of the area to prevent spread of the contamination. Check if you have been contaminated or if any of your PPE has been breached. If so follow exposure procedures. Remove any contaminated clothing and place it the biohazard waste. Wash your hands and post a sign on the door. Notify your supervisor of the incident and call ORS (4-8258) for assistance. If the situation involves an imminently life-threatening injury or has catastrophic potential, call 911. |
| Exposure Procedures | |
|---|---|
| Mucus Membrane | Flush eyes, mouth or nose for 15 minutes at eyewash station. |
| Other Exposure | For an area not protected by skin, wash with soap and water for 15 minutes (open wounds, sores, etc.) |
| Reporting | Report ALL injuries to the PI immediately and reported to the Office of Risk Management at [email protected] IMMEDIATELY FOLLOWING THE OCCURRENCE. Exposures that involve a bloodborne-pathogen or recombinant DNA also need to be reported to the Office of Research Safety at [email protected]. If the injury requires immediate medical attention, call GWPD at 202-994-6111 or call 911. |
| Medical Monitoring | Seek immediate medical evaluation, treatment, and post exposure follow-up at the Employee Health Office at GWU Hospital (900 23rd St., NW, Suite G-1090, Phone: 202-715-4275). Students should go to the Students Health Office at Marvin Center. After hours treatment can be received at the GWU hospital emergency room. |
| Stability | |
|---|---|
| Disinfection | TB is fairly resistant; amphyl and other phenol soap mixtures and 0.05 % to 0.5% sodium hypochlorite can be used for surface disinfection. Higher concentrations of chlorine are required for efficacy against TB. 10% bleach solution can be used as well |
| Inactivation | UV light can be used for surface disinfection, most bacteria are sensitive to moist heat (121°C for at least 15 min). Mycobacteria are easily killed by heat (> 65 °C for at least 30 min). |
| Survival Outside Host | Can survive for months on dry inanimate surfaces. Survives in cockroach feces for 8 weeks, sputum on carpet (19 days) and wood (over 88 days), moist and dry soil (4 weeks), and in the environment for more than 74 days if protected from light (possibly longer if in feces) |
| Personal Protective Equipment (PPE) | |
|---|---|
| Minimum PPE Requirements | At minimum, personnel are required to don gloves, closed toed shoes, lab coat, and appropriate face and eye protection prior to working with TB. Additional PPE may be required depending on lab specific SOPs. Higher containment levels will require donning scrubs and wearing respiratory protection. |
| Additional Precautions | Due to the modes of transmission, respirators may be required when working with TB. Fit testing and training is required. Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Wash hands with soap and water after removing gloves. |
| References | |
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